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Matrices for Cell Culture – A discussion about being clingy
Last week, we finished our Ask the Expert discussion on Matrices for Cell Culture – How to develop healthy attachment. Several questions were asked about matrices for differentiation, clinical grade matrices, 3-D matrices, lack of attachment with matrices, matrices that don’t require enzymes and whether matrices are autoclavable.
Many of the common cell types we use are robust and grow on cell culture treated plastic. However there are many cell types that have difficulty attaching and/or spreading on cell culture treated plastic. In other cases, cells may attach but not differentiate unless the attachment surface correct. Thesewere the topics covered in our last Ask the Expert session on Matrices.
This session, sponsored by Life Technologies and hosted by Timothy Fawcett, Ph.D. was a good discussion and with such a broad topic, we had quite a range of questions. Dr. Fawcett who has been in biotechnology for over 30 years, provided real hands-on suggestions that readers could benefit from right away.
Question topics included:
- Matrices for differentiation
- 3-D Matrices
- Clinical grade matrices
- Lack of attachment
- Matrices that don’t require enzymes
- Are matrices autoclavable
I have selected a few of the submitted questions and answers to include below. For a full list of questions and answers, please see Ask the Expert discussion on Matrices for Cell Culture – How to develop healthy attachment.
What are the differences, advantages/disadvantages to 3-D matrices?
Lets start with the advantages. When we grow cells the way most people do, by placing them in a dish and allowing them to attach we are growing cells in 2D. As you are aware few cells in the body grow in 2D, they actually grow in 3D. The idea behind 3D culture is to mimic the natural environment of the cell most closely making cell cultures more authentic in both structure and function. Cells growing in 2D have unlimited access to nutrients from the media above and the ability to remove waste products directly into the media. We also now know that cell-cell attachment and cell-matrix attachment are signal transducers and affect gene expression. As an example, Dr. Sangeeta Bhatia at M.I.T. has developed a system where rat hepatocyte cells are placed to mimic the natural organization of liver cells and has built a complete miniaturized ex vivo liver for drug metabolism studies (The Scientist May 1, 2013). Her approach is slightly different than 3D culture but it does point to the cell organization-funtion relationship. Others have shown how intestinal cells grown in 2D do not uptake blood pressure drugs because the bottom of the cells is where uptake occurs. In 2D cultures the bottom portion of the cell is not structurally relevant for uptake. In 3D culture uptake occurs.
On the downside, people have found some disadvantages to 3D culture but these disadvantages are being overcome by innovation. Some matrices are made from animal origin components which may make implementation for clinical work difficult. Some matrices made from tissue such as basement membrane extracts, can contain unknown or unwanted components like growth factors or viruses. Other matrices allow for attachment but not efficient removal of the cells making assay development difficult. To overcome these problems Gibco’s AlgiMatrix 3D culture System are completely animal origin free. As the name implies, AlgiMatrix 3D is made from algae and once the cells are grown, the 3D matrix can be dissolved using a dissolving buffer, liberating the cells for assays or whatever is needed. Other approaches to minimize these potential problems have resulted in matrix-free 3D culture. N3DBIO’s Bio-Assembler System actually levitates cells causing them to cluster together as groups making them have 3D contact without using a physical matrix. N3DBIO accomplishes this by providing a solution containing nanomagnetic particles that are incubated with the cells in culture. During a several hour incubation the magnetic particles are taken up by the cells. Once a supplied magnet is suspended above the wells the cells levitate together and grow as a cluster of cells in 3D.
How do matrices affect differentiation? Is there a way to control this?
Yes they do. One of the major reasons people use matrices is to maintain or promote differentiation. Years ago attachment was thought of as simply that…now we know attachment proteins in a cell contacting the proper matrix is a survival signal and a differentiation signal. Many of the different attachment proteins in a cell act as signal transducers that alter gene expression pathways in a cell. This is one reason why you read so much about 3D culture. Most cells do not live in 2D but in 3D and allowing them to grow in a more natural way causes cells to do things in 3D that they can not do in 2D. I often do experiments with a pheochromocytoma cell line that will differentiate into neuronal like cells if plated on a positive charged dish.
Can you recommend any matrices that don’t require enzymes during passaging. I am using iPSCs.
This is a good question. You know most of the matrices out there do require some sort of enzymatic digestion if your goal it to obtain single cells. Some matrices are such that the matrix can be dissolved to liberate the cells for assays or passaging. One example is Life Technologies AlgiMatrix 3D where a tri-sodium citrate solution is used to solubilize the matrix allowing cell isolation. Another approach is to use something like Versene which is a Ca/Mg free buffer with 0.43 mM EDTA. Versene chelates the Ca in media and buffer, and its use causes the attachment proteins do disassociate somewhat and can help some cell types loose attachment without using an enzyme. Primorigen Biosciences producers of StemAdhere XF allows for the growth of stem cells and iPSCs and non-enzymatic release of cells with a cell release buffer. Finally I found an interesting paper that may be pointing to the future for stem cell culturing. A Nature Communications 2013, Vol 4:1335 publication entitled, “A Thermoresponsive and Chemically Defined Hydrogel for Long-Term Culture of Human Embryonic Stem Cells” by Rong Zhang et al. These gels permit gentle reagent-free passaging using using temperature as a means to dissociate the matrix and allow passaging without enzymes.
Don’t miss next week’s Ask the Expert session –
“Moving your Cell Therapy from Concept to Product: Ask our Expert about navigating funding and grant writing, partnering with organizations, and the regulatory process,” hosted by Neil Littman, the Business Development Officer at the California Institute for Regenerative Medicine (CIRM).
Starts Monday, August 19th!
About CIRM: CIRM was established in November 2004 with the passage of Proposition 71, the California Stem Cell Research and Cures Act. The statewide ballot measure, which provided $3 billion in funding for stem cell research at California universities and research institutions, was overwhelmingly approved by voters, and called for the establishment of an entity to make grants and provide loans for stem cell research, research facilities, and other vital research. In 2012, CIRM adopted an “Industry Engagement and Commercialization Plan,” which serves as CIRM’s blueprint for continuing to support Proposition 71’s mission by engaging industry and supporting commercialization of CIRM’s funded research. You can find more information about CIRM here: http://www.cirm.ca.gov/.